Ionizers of a corona discharge type are widely used for controlling static electricity in air, such as cleaning of clean rooms and electric discharge from floating particles, as well as electric discharge from works.
FIG. 14 shows a discharge electrode bar of a currently available DC ionizer. The discharge electrode bar 1 has an elongated tubular case 2. Cylindrical nozzles 3a, 3b, each encircling a discharge electrode, are attached to the case 2 at intervals along the lengthwise direction of the case 2.
In the conventional discharge electrode bar 1, a high voltage source unit 4 or a control unit 5 is located between every adjacent nozzles 3, 3, and clean gas from each nozzle 3 is supplied through a flexible tube 6 extending inside the case 2. In FIG. 14, positive pole nozzles of the DC discharge electrode bar 1 are labeled with 3a, and negative pole nozzles are labeled with 3b. 
In the conventional discharge electrode bar 1 in which the nozzles encircle the discharge electrodes, the nozzles charge with electricity of the same polarity as that of the discharge electrodes. Therefore, here is the problem that the nozzles attenuate the electric field around the discharge electrodes and hence reduce the yield of ions.